An Improved Aspirating Probe for Total-Temperature and Total-Pressure Measurements in Compressor Flows

Abstract

The aspirating probe originally designed by Epstein and Ng at MIT was modified by replacing the two platinum-coated tungsten hot wires normally used with platinum–iridium alloy wires. The resulting improved unsteady total pressure and total temperature resolution of the modified probe is demonstrated. Flowfield measurements were made downstream of NASA Rotor 37 for a part-speed operating condition to test the performance of the probe. Time-resolved blade-to-blade total temperature and total pressure as calculated from the two platinum–iridium hot-wire voltages are shown. The flowfield measurements are compared with independent measurements of total pressure with high response transducers and total temperature calculated from laser anemometer measurements. Limitations of a more often used unsteady temperature data reduction method, which involves only one aspirating probe hot-wire voltage and a high-response pressure measurement, are discussed.